1. Field of the Invention
The present invention relates to a portable timepiece having a structure of holding a crown so as not to be rotated unpreparedly.
2. Description of the Prior Art
There is a portable timepiece adopting a structure of locking a crown by utilizing mesh of screws (the structure is referred to as screw lock in the specification) such that the crown is not rotated unpreparedly in carrying the portable timepiece.
The screw lock structure is constituted by a structure of attaching a winding stem pipe to a case body including a timepiece movement and screwing a female screw portion of a main body portion of the crown fitted to a case back outside projected portion to a male screw portion formed at an outer periphery of the case back outside projected portion of the pipe. Thereby, normally, the crown can be locked by screwing the main body portion of the crown to the outer periphery of the case back out side projected portion. Further, in operating the timepiece movement, a winding stem arranged on an inner side of the winding stem pipe can be operated to rotate in a state of pulling to move the crown after disengaging the main body portion of the crown from being screwed to the male screw portion.
According to the portable timepiece of the background art having such a screw lock structure, generally, by brazing the winding stem pipe to the case back, waterproof of a portion of attaching the winding stem pipe is achieved (refer to, for example, JP-A-57-46181).
Otherwise, there is also known a portable timepiece in which a winding stem pipe is provided with a male screw portion separately from a male screw portion screwed with a crown, the separately provided male screw portion is screwed to a pipe attaching hole of a case back, and in accordance with the screwing operation, a waterproof packing is pinched between the case back and the winding stem pipe to thereby achieve waterproof of a portion of attaching the winding stem pipe (refer to, for example, JP-A-2004-245594).
According to the portable timepiece having the screw lock structure, there is a case in which in accordance with operating to rotate the crown repeatedly, the female screw portion of the crown and the male screw portion of the winding stem pipe screwed to each other are worn or ground. Thereby, a function of screw lock is deteriorated.
When such a situation is brought about, in the case of the portable timepiece of JP-A-57-46181 in which the winding stem pipe is brazed to the case back, interchange of a part around the crown in accordance with removing the winding stem pipe from the case back cannot be carried out. Therefore, a timepiece exterior assembly including the case back is obliged to be interchanged and an improvement thereof is requested.
It is conceived that according to the timepiece in which the winding stem pipe is screwed to the case back, in principle, a part at a surrounding of the crown including the winding stem pipe can be interchanged. However, also in the constitution, at each time of screwing the crown to the winding stem pipe or disengaging the crown from being engaged in this way, the winding stem pipe is operated with rotational force. In accordance therewith, there is a concern of deteriorating waterproof performance by the waterproof packing by loosening the winding stem pipe from being screwed to the case back.
As a countermeasure therefor, there is a case of filling an adhering agent to portions of the winding stem pipe and the case back screwed to each other. When the winding stem pipe and the case back are adhered in this way, it is difficult to remove the winding stem pipe from the case back and actually, a part at a surrounding the crown cannot be interchanged. Thereby, when the screw lock function is deteriorated, a timepiece exterior assembly including the case body is obliged to be interchanged and therefore, an improvement thereof is requested.